1. Field of the Invention
The present invention generally relates to improving electrical switches.
2. Description of the Related Art
Electrical switches are commonly used in many devices, such as, microelectromechanical systems (MEMS). In the MEMS example, such devices often utilize switches to selectively make contacts to route electrical signals through the MEMS devices to facilitate the use and control thereof. Such switches are typically expected to have a fixed lifetime, such that any problem that interferes with the operation or performance of the switch typically effectively destroys the MEMS device. For example, oxidation on contacts of the switch may degrade the electrical performance of the switch. Similarly, contact pad wear due to use of the switch may also decrease the performance and/or the life of the switch. Further, particles or other contaminants may also interfere with switch performance.
U.S. Pat. No. 7,106,066, issued to Ivanciw, et al. (hereinafter Ivanciw), discloses a circuit that may be coupled to a switch for sensing a performance parameter of the switch and providing a time-varying action if the sensed performance parameter is outside of some threshold value, such as applying a time-varying voltage to the control element of a closed switch to cause a motion of an end of a beam of the switch against a corresponding contact pad.
The motion disclosed by Ivanciw is taught to include a back-and-forth (lateral) movement of the beam along a plane parallel to and in contact with the contact pad (e.g., a rubbing motion), or an up-and-down movement of at least a portion of the beam perpendicular to the contact pad, such that the beam taps the contact pad. The time-varying voltage of Ivanciw can increase the lateral displacement (or movement) of the beam and the amount of the beam that contacts the contact pad. For example, Ivanciw teaches that a greater voltage will increase the lateral movement and the degree by which the beam contacts with, and thereby rubs, the contact pad.
The switches disclosed by Ivanciw generally provide plate-to-plate contact between the switch element and the contact pad (where relatively large contact areas engage in a predominantly perpendicular manner) or an active-opening “teeter-totter” switch (where an electrode is placed on either side of a pivot point for controlling the position of a beam of the switch). In the plate-to-plate switch examples, however, any rub that is generated is relatively small due to the configuration of the switch, thereby limiting any effect provided by the circuit controlling the switch. Moreover, the relatively large contact areas continues to promote the stiction problem. In the “teeter-totter” switch configuration, any rub of the contact element is again limited due to the linear configuration of the beam of the switch.
In addition, the switches disclosed by Ivanciw rely on electrostatic attraction between the beam/plate of the switch and an electrode disposed thereunder to pull the beam/plate into a closed position. Such switch closing electrode configurations undesirably utilize relatively high voltages, thereby limiting their application in devices where much lower voltages are required. For example, Ivanciw discloses switches having closing voltages of greater than 40 Volts, and operational voltages of up to almost 70 volts.
Thus, there is a need for an improved switch.